In a large mixing bowl, add the diced beef, paprika, a generous pinch of salt and cracked black pepper. Toss until the beef is well coated. Sprinkle over the plain flour and toss again to coat lightly. This will help thicken the sauce as it cooks.
To the slow cooker add the coated beef, followed by onions, garlic, tomato paste, passata, red wine vinegar, beef stock, and bay leaves. Stir everything together to combine.
Cover and cook on low for 7-8 hours or high for 4-5 hours, until the beef is tender and the sauce has thickened slightly.
About 60 minutes before the end of cooking time, stir in the mushrooms. Cover and cook.
Stir in the fresh gnocchi, ensuring it's submerged in the sauce. Cover and cook for the remaining 20-25 minutes, or until the gnocchi is soft and cooked through.
Remove the bay leaves, give everything a gentle final stir, and serve hot. Top with a spoonful of sour cream and a sprinkle of fresh parsley if desired.
Freezer-friendly: Cool completely, then portion into airtight containers and freeze for up to 3 months. Defrost in the fridge and reheat gently, adding a splash of stock or water to loosen the sauce if needed.
Oven-friendly: Preheat the oven to 320°F / 160°C (fan forced). In a large Dutch oven or oven-safe casserole dish, add coated beef, onions, garlic, tomato paste, passata, red wine vinegar, beef stock, bay leaves, and seasoning. Stir to combine. Cover with a lid and bake for 2.5-3 hours, or until the beef is tender. Stir in mushrooms and return to the oven for 15 minutes, then add gnocchi and cook for a further 20-25 minutes, or until gnocchi is soft and the sauce is thickened.